Linq 集成化查询（1）

 近一段时间抽空看了一下Linq的知识，学习了一下，也分享给大家，以后使用也方便，用过Linq的程序员可能都感觉到得到，Linq和sql语法简直就一样。所有会SQl的学习LInq就很容易了。

 废话少说，首先我们构造一个数据源方便说明代码

Student[] strAry =
            {
                new Student("张三","男",20),
                 new Student("张20","女",20),
                new Student("张一","男",15),
                new Student("张花","女",10),
                new Student("张美丽","女",20),
                new Student("张坏","男",18),
                new Student("张蓝蓝","女",20),
            };

　1.普通查询语法from a.....in  集合 where .....select a 如果需要对集合进行简单的分组 为 from a in 集合 where 条件 group a by a.属性 排序字段

 var query1 = from st in strAry group st by st.strSex;
            foreach (var grp in query1)
            {
                System.Console.WriteLine(grp.Key);
                foreach (var val in grp)
                {
                    System.Console.WriteLine("\t{0}", val);
                }
            }

var query2 = from st in strAry
                         group st by st.intAge into stuGrp
                         orderby stuGrp.Key descending
                         select stuGrp;
            foreach (var stg in query2)
            {
                System.Console.WriteLine("{0}岁学生：", stg.Key);
                foreach (var st in stg)
                {
                    System.Console.WriteLine("\t{0}", st);
                }
            }

　　2，使用linq同时查询两个集合，其中一个集是另一集合的属性 这里可以使用嵌套查询

  

 Student[] strAry2 =
            {
                new Student("张三","男",20,new List<Socre>{new Socre("语文",120),new Socre("数学",60),new Socre("英语",55)}),
                new Student("张一","男",15,new List<Socre>{new Socre("语文",50),new Socre("数学",50),new Socre("英语",90)}),
                new Student("张花","女",10,new List<Socre>{new Socre("语文",80),new Socre("数学",60),new Socre("英语",88)}),
                new Student("张美丽","女",20,new List<Socre>{new Socre("语文",30),new Socre("数学",40),new Socre("英语",80)}),
                new Student("张坏","男",18,new List<Socre>{new Socre("语文",100),new Socre("数学",60),new Socre("英语",60)}),
                new Student("张蓝蓝","女",20,new List<Socre>{new Socre("语文",90),new Socre("数学",30),new Socre("英语",86)}),
            };

            var query3 = from str in strAry2
                         from strc in str.Socres
                         where strc.dblscore > 60
                         group strc by str.strName;//group 后面的句子是分组形成的数据项
            foreach (var stg in query3)
            {
                System.Console.WriteLine(stg.Key);
                foreach (var st in stg)
                {
                    System.Console.WriteLine("\t{0}", st);
                }
            }